Completely untested, but this should work:
View positiveButton = findViewById(R.id.positiveButton);
RelativeLayout.LayoutParams layoutParams =
(RelativeLayout.LayoutParams)positiveButton.getLayoutParams();
layoutParams.addRule(RelativeLayout.CENTER_IN_PARENT, RelativeLayout.TRUE);
positiveButton.setLayoutParams(layoutParams);
add android:configChanges="orientation|screenSize" inside your activity in your manifest